Deno KV: Key/Value database

Warning: This is an unstable API that is subject to change or removal at anytime.
Deno KV is a key/value database built in to the Deno runtime, and works with zero configuration on Deno Deploy. It's great for use cases that require fast reads and don't require the query flexibility of a SQL database.

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Open the default database

const kv = await Deno.openKv();

Define an interface in TypeScript for our data

enum Rank {
  Bronze,
  Silver,
  Gold,
}

interface Player {
  username: string;
  rank: Rank;
}

Create a few instances for testing

const player1: Player = { username: "carlos", rank: Rank.Bronze };
const player2: Player = { username: "briana", rank: Rank.Silver };
const player3: Player = { username: "alice", rank: Rank.Bronze };

Store object data in Deno KV using the "set" operation. Keys can be arranged hierarchically, not unlike resources in a REST API.

await kv.set(["players", player1.username], player1);
await kv.set(["players", player2.username], player2);
await kv.set(["players", player3.username], player3);

The "set" operation is used to both create and update data for a given key

player3.rank = Rank.Gold;
await kv.set(["players", player3.username], player3);

Fetch a single object by key with the "get" operation

const record = await kv.get(["players", "alice"]);
const alice: Player = record.value as Player;
console.log(record.key, record.versionstamp, alice);

Fetch several objects by key with "getMany"

const [record1, record2] = await kv.getMany([
  ["players", "carlos"],
  ["players", "briana"],
]);
console.log(record1, record2);

List several records by key prefix - note that results are ordered lexicographically, so our players will be fetched in the order "alice", "briana", "carlos"

const records = kv.list({ prefix: ["players"] });
const players = [];
for await (const res of records) {
  players.push(res.value as Player);
}
console.log(players);

Delete a value for a given key

await kv.delete(["players", "carlos"]);

The Deno.KvU64 object is a wrapper for 64 bit integers (BigInt), so you can quickly update very large numbers. Let's add a "score" for alice.

const aliceScoreKey = ["scores", "alice"];
await kv.set(aliceScoreKey, new Deno.KvU64(0n));

To prepare an atomic transaction to update the score, first we need to check if the score has been modified since we read it. We can use the versionstamp to check if the value has been modified since we read it.

const aliceScoreEntry = await kv.get(aliceScoreKey);
const atomicCheck = {
  key: aliceScoreEntry.key,
  versionstamp: aliceScoreEntry.versionstamp,
};

Add 10 to the player's score in an atomic transaction

const res = await kv.atomic()
  .check(atomicCheck)
  .mutate({
    type: "sum",
    key: aliceScoreKey,
    value: new Deno.KvU64(10n),
  })
  .commit();

Check if the transaction was successful

if (res.ok) {
  const newScore = (await kv.get(aliceScoreKey)).value;
  console.log("Alice's new score is:", newScore);
} else {
  console.error("Transaction failed ");

Optionally, implement retry logic or handle the conflict

Run this example locally using the Deno CLI:

deno run --unstable-kv https://docs.deno.com/examples/scripts/kv.ts

Deno KV: Key/Value database

Additional resources

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